On Tue, Jun 5, 2018 at 10:39 AM Noam Postavsky <npostavs@gmail.com> wrote:

> On 5 June 2018 at 13:30, Ryan Thompson <rct@thompsonclan.org> wrote:
> >
> > The following code throws an error:
> >
> > (progn
> >    (string-match "h.*o" "hello")
> >    (format-spec "This sets the %s" (format-spec-make ?s "match data"))
> >    (match-string 0 "hello"))
> >
> > This is because the implementation of "format-spec" uses regular
> > expressions internally, and does not save the match data and restore it
> > afterward.
>
> (elisp) Match Data:
>
> Notice that all functions are allowed to overwrite the match data
> unless they’re explicitly documented not to do so.
>

Wow, I was not aware of that. This seems... really fragile. In any case, I
suppose the behavior is as documented, so you can close this bug.